The present invention relates to a process for producing a thin-film solar or photovoltaic module as well as to separating means for use in this process.
One possibility for producing thin-film solar modules or thin-film photovoltaic modules comprising a plurality of solar or photovoltaic cells disposed in parallel on a common substrate, which are produced and electrically interconnected by a plurality of cell-overlapping coating steps and coating-separation steps during cell production has already been described in U.S. Pat. No. 4,243,432. In that specification, CdS--Cu.sub.x S solar cells are produced in that a glass substrate is always completely provided with deposited individual layers, one upon the other. The layers in form of thin films mainly comprise a hard contact layer of SnO.sub.x serving as the lower electrode and a pn double layer of CdS--Cu.sub.x S disposed on it as well as a further contact layer serving as the upper electrode. Cuts performed between the individual thin film deposition steps have been provided to subdivide the cell-overlapping substrate film coating into individual cells, on the one hand, and to electrically series-connect the cells of a substrate, on the other hand. For serial interconnection of the cells, the cuts are provided such that the upper electrode of a cell 1 contacts the lower electrode of following cell 2, however, is separated from the upper electrode of cell 2. This scheme is continuously repeated over the whole substrate length. Various methods for separating the individual layers have been suggested in this U.S. patent, inter alia by ultrasonic techniques, and it has been stated that the pn layer may also be separated for instance by means of a rotating or a non-rotating cutting tool.
In U.S. Pat. No. 4,315,096, a similar process has been disclosed for CdTe and CdS layers wherein the separation cuts having a width of between 5 .mu.m and 100 .mu.m are also produced either by mechanical methods not defined in detail or by means of laser beams. U.S. Pat. No. 5,501,744, also, refers to the production of CdTe and CdS solar cells. According to U.S. Pat. No. 5,501,744, the modules are processed by means of a tool head which is movable both in transversal and longitudinal direction relative to the substrate. The tool head includes lasers, arranged side by side, sandblast blowers or deposition means which are obliquely directed to the substrate and, preferably, do not contact the substrate. After processing the substrate in longitudinal direction, the head is displaced in transverse direction to a new starting position for longitudinal movement. During the course of this transverse movement, the processing units are not activated.
As yet, however, commercially traded silicon solar cell modules have not, as a rule, been fabricated in accordance with the above process of U.S. Pat. No. 4,243,432. Rather, they have been made of individual cells which are interconnected by means of soldered-on metal strips. Modules comprising CdS--Cu.sub.x S solar cells have not so far been produced on an industrial scale in accordance with the above-referenced process of U.S. Pat. No. 4,243,432. The same applies to CdS/CdTe solar cells which have, for a considerable time been considered as promising and which include a front contact of a transparent TCO layer, mostly in the shape of a so-called ITO layer. As to the production and the structure of such an individual solar cell, explicit reference is made to European Patent No. EP 0,535,522, which corresponds to U.S. Pat. No. 5,304,499.